The usual way of blow molding double-walled boxes limits their depth to one-half their narrowest width, which also limits their potential uses. Although several suggestions have been made for overcoming this limitation, none of them have been practically successful for deep boxes.
We have discovered a way of molding a generally rectangular double-walled box in two halves that can be oriented relative to a mold cavity and core so that the usual depth limitation does not apply. Our box halves can be joined together to form a completed box with ample depth, and a hinged cover for the box can be trapped between the assembled box halves. The many possible uses for such a box include filling its interwall spaces with fire resistant insulation to make a fire resistant box or filling with thermal insulation to make an ice box.